The present invention is directed to bicycle brakes and, more particularly, to a hydraulic rim brake for a bicycle.
Some bicycle brakes comprise first and second brake arms pivotably mounted to a bicycle frame member such as front fork or rear seat stay of the bicycle frame. Each brake arm includes a brake arm mounting portion for mounting the brake arm to the bicycle frame member, a brake pad mounting portion, and a control interface portion. The brake arm mounting portion is disposed between the brake pad mounting portion and the control interface portion such that the brake pad mounting portion is disposed below the brake arm mounting portion when the brake arm is mounted to the bicycle frame member. Such brakes may be cable operated or hydraulically operated.
U.S. Pat. Nos. 3,338,337 and 3,899,057 disclose examples of hydraulically operated brakes. As shown in those patents, a piston assembly is coupled to the control interface portions of the first and second brake arms. The piston assembly comprises a piston disposed within a hydraulic chamber formed in a housing, wherein the housing includes first and second axial ends. The piston includes an output shaft that extends from the first axial end of the housing. The output shaft is connected to the control portion of the first brake arm, and the second axial end of the housing is connected to the control portion of the second brake arm. During operation, hydraulic fluid is introduced into the hydraulic chamber to cause the piston to move axially towards the first axial end of the housing, thereby causing the output shaft to extend further from the first axial end of the housing. As a result, the control portion of the first brake arm moves away from the control portion of the second brake arm, thereby causing the brake pad mounting portions of the first and second brake arms to move towards the wheel rim so that brake pads mounted to the first and second brake arms contact the wheel rim.